Method of testing vision



Oct. 9, 1928.

J. Z. A. DENINSON METHOD OF TESTING VISION Original Filed May 28. 1921 4 Sheets-Sheet s u e MEMORANDUM AsrlGMA-nsn Hon. Axis vim' Axis smAsnsMus QFLEFT EYE nA're 0F mAeNosis 192i.

:Nvt-:N25 JffmA// elw/afm BY l/ MWI( ATTORNEYS Oct. 9, 1928.

J. Z. A. DENINSON METHOD OF TESTING VISION 4 Sheets-Sheet 2 Original Filed May 28. 1921 llll sllmZ.

Oct. 9, 1928. 1,686,962 J. Z. A. DENlNsoN METHOD OF TESTING VISION Original Filed May 28. 1921 4 Sheets-Sheet 5 INVENTOR BWM/7%# ATTORNEY 3 Oct. 9, 1928. 1,686,952

.J. z. A. DENlNsoN METHOD OF TESTING VISION 4 Sheets-Sheet 4 Original Filed May 28 1921 ENTOR.

ATTORNEYS.

.50' method and instrument.

Patented Oct. 9, 1928.

[y jul/UNITED.STATES --PATEzN-T OFFCBff' r anco-B v2.1L*miiarlasoia,or.Naw Yoan, N. Y.

I vMy invention relates to a new and improved method-and instrument for testin'gthe vision.

.Thedefects of vision which can .be correct-- .ed by optometrical means are" astigmatism, strabismus,` myopiaand hypermetr'opia and 'y other defects of accommod'ation. lThe `opto- 4- `metrical instruments which have heretofore been `designed and used have depended, in

testing the defects in vision, upon a ser1es` of graduated lens'es'or thel like whichi were"I successively brought' in Ifront' ofthe eye-of the patient. Theseinstruments'could never give' absolutely correct results, because'they merely informed the physician' or 'opto- Ametrist that thed'efect of the eye of the patient in any particular respect wasbetween one point and another,point,y corresponding to the two lenses or thelike,- which-the patient stated approximated most closelyj tofc'orrect-"- ing `his vision. n

-\Accord1ng to my'inventlon the exact point at which the vision of the patien'tisproperlyl l `corrected' can be'r'eadily ascertained.

f Anotherobject of my invention is to prolpa'tien'ts vision can be supplied to the physician or Optometrist. i Another object of my invention is to provide a mechanism whereby the-patienthimself without being interrogated by' the physician can make 'a consecutive record' which will completely inform the physician or Optometrist of the conditionv of his vision. Another object of'my inventionis to pro` vide an instrument which willjnot ldepend upon a' series' ofy expensive `and carefully vgraduated lenses or similar refracting means. Another object of my invent-ion is to provide an -instrument;lvhich by a series of adi ustments will give the exact condition ofthe Apatients vision in each and every respect, .so that a series of `different instruments or attachments willnot be necessary. l

Other objects of my invention will be set forth in the following description and drawings which illustrate a preferred embodin jment thereof.' Y

vide a method wherebyan exact chart'of the imap-.0F @am ,v1-sra@ 1 Appliao med mi@1921;'seria1Naj47a517. 'Renewed rune 5, 1.928.

matism can be detected and measured." 7'

` Fig.` 4 is a top view of the instrument showing means whereby the patient canv make his own record.'

Fig. 5 is an yelevation of F ig. 4. c

Fig. 6 is an end view of Fig. 5 as seen from the left'hand side of Fig. 5, the head support 'being omitted for the sake of clearness.

F ig. 7 is also a'n end View of Fig. 5,"but` as seen from the right-hand side.

Fig. 8 is a detail .topvew showing thescale y -for recording the condition of astigmatism. Fig. 9 isa front View of Fig. 8.

lFig'. 10' is an end View of Fig. 9taken4 at the right-hand side of Fig. 9.

Fig. 11 is a bottom View of Fig.19,

Fig. 12 shows an end View of the prisms used in the instrument.

Fig. 13 is a front View of Fig. l2.

` Fig. `14=`is a horizontal central section of 1 Fig. 13.

Figure 15 is an elevation of the screen used in my instrument. j

Fig. 16is 4an end View of Fig. 5.

Fig 17 is an elevation of a special screen u sed for testing compound or mixed astigmatism.

Fig. 18 is another embodiment of Fi 17. The principle of my invention can Fe generally seen from the structure shown in Fig.

ures 1, 9, 13 and 15. It depends upon the following rinciple The visi le object which is used for testing the eyesight ofthe patient may be any small object whatever, that is rendered visible or luminous vby any means whatever. In this particular embodiment illumination is 'supplied by a small electric lamp 1 of the ordinary incandescent type which can be connected to any suitable source of current. The light emanating from the luminous object 1 which should always be of constant intensity, 'i's caused to pass through the screens 2 and 2 shown in Figs. 1 and 15, so that the light can pass through five openings made in thisscre'en 2. The central opening 5in screen 2 can be made of any. desired diameter, so -as to regulate the light supplied to the instrument.

It can be noted'that the opening 5 is central, and that the slits 3 are elongated 'and they are symmetrically disposed with revspect'to the central opening 5. These slits or openings in the screen or screens can be l of any' configuration.

A sheet of transparent glass 8 is held in a frame 4 and carries two prisms 7 and two prisms 8, so that as seen in Fig. 9, the center 5 of said circular sheet of glass 8 is on the same line as the center of opening 5 and the centers of the prisms are on the same horizontal lines as the centers of the slits 3. The glass 8 and the four prisms may be ground out of one piece of glass, which is preferably chromatic.

As can be seen from Figs. 12 and 14, the two vertical prisms 8 consist essentially of cylindrical glass members aving surfaces which have been cut H by two planes which make equal angles with the optical axis of the instrument. This optical axis may be defined as the horizontal line between the opening in screen 2 and the central opening in the screen 2.

The two horizont-al prisms 7 may also be considered as cylindrical glass members which have been cut by two planes which also make equal angles with the optical axis of the instrument. Hence if perpendicular lines were drawn to the 'inclined faces of thel prisms 7 and 8 at the centralpoints of said inclined faces, these four perpendiculars if prolonged, would meet in a common point on the optical axis. In Fig. 1, the prisms are shown adjacent the eye of the observer, but they should be turned together with screen 2, so that the prisms face the light.

Hence as can be seen more particularly in Fig. l which shows the lamp 1, the screen 2',

and the holder 4 in two dierent positions, the corresponding positions of the various parts being shown by full lines and dotted lines respectively, if the eye of the observer is properly held, then the said observer will see five images of the luminous opening in screen or diaphragm 2. Of course, if the patient is suering from strabismus, he will not see live images but a number less than live, depending upon his condition, but it is preferable to first take up, in explaining this invention, abnormal conditions of the lens of the eye and if the patient is merely suffering from an improper adjustment of the ciliary muscle, there will always Ibe a position in which he will see live images of the dull or luminous object which serves asi/.the means for supplying said images. In the position indicated by the full lines in Fig. l, the eye of the observer is shown as placed in the position in which he can see the five images of the object.

In order to test the range of accommodation of the patients ciliary muscle and to detect myopia or hypermetropia, the observer preferabl keeps his eye stationary :while the parts of t e instrument are moved.

In Fig. l, the position of the eye designated by the line marked 0 shows the position ofthe lens when the eye is at rest. The position marked 7 is the position of the retina and the position marked 7 is the point of convergence of the said rays from the inclined faces of the prisms, so that if a white screen were placed in position 7, a single image would be formed.

The screen 2 is preferably always kept at the same distance from the luminous object 1 as clearly appears from Fig. 1, but the holder 4 together with the prisms 7 and S and the screen 2 which are all held therein, is now preferably moved through a series of positions as indicated by the corresponding positions 1--7 shown in Fig. l. In these positions, the point of convergence before mentioned is no longer at the optical center of the patients lens and so the ciliary muscle of the patient is compelled to exert itself so as to accommodate the lens of the eye in order to enable the patient to still see the live separate images of the object. For example, the holder 4 is first moved to the position indicated by zero in Fig. 1 in beginning the examination and this corresponds to the punctum remotum, that is, the point in which the ciliary muscle of the normal eye is preferably relaxed, as for example when the patient is gazing at the sky or some very distance object. Of course, the zero position is not the same for each eye, as it depends on the powers of accomodation of the eye examined. The instrument will be provided with a horizontal scale to indicate the movement of the lamp 1 and screen 2 which may be considered as jointlycomposing a visible object, namely, the opening in screen 2. At each one of its positions the luminous object will be held stationary, while the holder 4 will have to be moved to a position depending upon'the vision of the patient, in order to enable the patient to again see the five images. For example, when the object is held on the zero point of the scale, the operator will move the holder 4 until, for example, in the case of the eye considered as now being examined, the said holder will be moved to the point indicated by zero in Fig. 1. This point will indicate the accommodation for remote vision of the patient.

Underneath the instrument a revoluble cylindrical member 10 will be mounted upon any suitable axle 11 and this may be revolved in opposite directions as indicated by the two arrows shown in Figure 1. This recording member 10 may be provided with an externally located chart of paper or the like, upon which a record may be made. Tomake the record, the chart shown in Fig. 2 is placed around the recording cylinder 10 and held there by any suitable means, The chart 12 is so mounted on cylinder 10 that the line marked binocular axis is parallel to the axle 11, and one of the ends of said chart is on the top line of cylinder 10.

The holder 4 slides to and fro upon a guide or guides 51, or any equivalent means, and

the position indicated'by zero in Fig. 1l is the furthest point to'fWhich the holder 4 can be moved to the right, While the position indicated by 7 in Fig. 1 shows the furthest posi? tion to which it is moved to the left, in the case of the particular eye considered as now being examined.

` The frame 4 is provided With a vertically held pencil or sharp pointed member 46 or other suitable marking means, and the recording drum can be moved vertically up and down in suitable guideways later to be described, so that When the frame 4 is in any position, the said position can. be recordedupon the chart 12 by moving the recording member 10 upwardly when the before mentioned pencil or piercing member or the like, Will make a suitable record'upon the chart 12. This vertical indicating member is diagrammatically shown in Fig. 1 by the vertical line from 7 in the left scale.

If the holder 4 is at the point marked zero in Fig. 1, then the indicating member will make a mark on the chart 12 corresponding to the zero point thereo-f and this may be the starting point in testing all eyes. The recording cylinder 10 is now re-volved about the axle 11 through a certain arc. This arc, of course, Will be oneseventh of 360o in this particular instance, but of course, the instrument may be used with any number of.

graduations on the scale for indicating the movement of the object viewed and With any corresponding turn of the recording cylinder 10. The object viewed is now moved to the position marked 1 and the holder 4 is again moved until the patient sees the five images. In the case of the eye which is considered as being examined, the position 1 of the frame 4 is supposed to correspond to position 1 of the object viewed. The record is again made in the manner before indicated. In this manner, a graph is indicated by means of a series of separated points upon the chart 12 and this graph indicates the condition of the patients eye. The position of the frame marked 7 indicates the punctum proximum or the limit of near vision for the eye supposed to be under examination.

If the patient is suffering from astigmatism he will not see all the four lateral images in the form of a crossuntil the proper adjustment is made of the slits 3 in the screen 2. In

'orderto determine the correction astigmatism the special screens shown in Figs. 17 and 18 may beiused. One of the' s'cr'eensshown in F igs.-17 and 18 'can "bef substituted f or the screen `2 shown in Fig. 1 in frame 4. The

lvv`l` screen 14 shown in Figui17`, vvhich'may 'be calledI `the astigmatisn'nk1screen,l lis provided the screen 14 so that the light can still pass through the prisms. The screen 14 is prof vided with four holes 18 which register `with the central portions of the prisms. By revolving the opaque member 16, the illumination can be cut of from either the two verti* cal openings 18 or the two horizontal openings 18.

If the patient is astigmatic, then he will not see the lateral images along two perpendicular lines, but lie will see them along lines which are relatively inclined toward each other. By revolving the annular holder 4 whichv carries the prisms and screen and is mounted in frame 4, the four lateral images finally designate two perpendicular lines, and the amount `of turn necessary to produce this, and which measures'the astigmatism, can be een from the scale 53 on frame 4 shown in In the screen 2O shown in Fig. 18, there are two opaque members 16 mounted as before mentioned and these are perforated at 19 and the supplemental screen 20 shown in Fig. 18 is provided With four arcuate slits 21. The central points of. the arcuate slits 21 correspond to the central points of the prisms 4,

since to make the completed test' for astigmatism the screen 2 is replaced by the screen 20. By properly disposing openings 19, astigmatism is corrected and other tests can be made.

In order to test for strasbismus, the frame 4 is turned around either on a horizontal or a vertical axis and the amount of the turning may be indicated by scales until the five images are seen by the patient. This is diagrammatically illustrated in Fig. 3.

The specific mechanism for putting into practice the principles and methods .before mentioned, is shown in Figs. 4-11. The object is mounted upon a base 22 which can Slide to and fro upon a suitable guideway 23. The guideway 23 is provided at the rear thereof with a pulley 24 mounted in a bracket 25. A cord 26 is secured to the rear end of the base 22 and this passes around the pulley 24 and then around pulley 26 and the drum 27, the axle of which is provided With a sprocket 28 that meshes with the broken spur gear 29. The sprocket 28 is connected to its shaft by any conventional clutch or paWl and ratchet construction, so that it engages and turns said shaft When revolved in one direction and does not engage it when revolved'in the other direction. The spur gear "29 revolves around the axle 30. "At the front ofl the frame 22 the other Aend of thelrope or` similar member 26is secured. l The other end of the rope 26 is secured tothe front of the frame`22 and'this runs around'the pulley 31.y Hence the frame 22 can be movedaivay from the head rest by revolving'spur gear 29.

ies

llll

The'jpa'tient canman'i'pulatef4 the handle 32` in the direction ofthe arrow shown in Fig.

V5, this direction being upward from the plane of the paper inv Fig. 6 and perpendicular thereto. The handle 32 is secured to an arm 33 `which is also connected to a shaft upon which the revoluble cam member 34 is mounted.V This cam member 34 has an arcuate inclined face 35 at the end thereof, so that when the cam member 34 is revolved, the drum 10 is raised since this drum 10 has its axle 1l in contact with the cam 35, so that the drum l() can revolve and can also be raised by the movement of handle 32. A spring 36 is provided to auton'iatically return the handle 32 and hence return drum 10 to its lower position when the operator releases the handle 32.

The arm 33 is also connected to the arm 40 which is pivotally connected to the gear 29, so that when the patient operates the handle 32, he automatically moves the lamp and this makes his own record upon the drum 10. The patient can also move the frame 4 and in this manner he can make a complete record of the condition of his own eye. This enables the examination of the patient to be completed Without being compelled to ask any questions, and this is extremely convenient il the patient is deaf.

In order to provide for differences between the pupils of the eyes of various persons, the 'following adjustment is provided The rail 23 is mounted upon a pin S which is pivotally mounted on a movable support S, the said support S being provided with an index member 60 which cooperates with 'a scale 61 at the base of the instrument. l

The instrument is provided at the head rest portion with a large opening through which the object can lbe seen by both eyes of the K patient, but a suitable screen or the like will be provided as is well known, to shut off the light from the eyes of the patient.

It is obvious that it the pupils of the patient are closer together than the normal or standard that the visual angle for an object at a given distance from the patient will be smaller than the normal, and similarly it' the pupils are further apart than the normal, this horizontal visual angle will be greater.

As can be seen more particularly in Fig. 5, the rail or guide 23 is connected to the pin t by means of a curved slide S which can slide freely to and fro within the rail'or guide 23 and is secured to a head attached to the pin S.

Hence the guide 23 and all the parts mounted thereon or connected thereto, such as the lamp and the frame, for example, can be swung vertically around the pin S and by moving the support to and fro, the distance ot the pivot point S from the eye of the patient can be varied, this distance being made smaller if the pupils of his eyes are too close together and vice versa.

Hence the guide 23 and the parts mounted thereon and secured thereto, are swung from one eye of the patient to the other, the eye of the patient which is not being tested being, of course, prevented from seeing.

l/Vhen the chart shown in Fig. 2 and upon a larger scale in Fig. 2b is to be used for making a record or graph of the condition of the patients eyesight, so as to determine Whether he is near-sighted or far-sighted and the direction of the binocular axis or other general conditions ot' the eye, said chart is placed so that either the left side or the right side thereof as seen in Fig. 2 for example coincides with the top of the cylinder 10 as illustrated in Fig. 1.

For example, if it is desired to test the right eye of the patient, then the right side of the chart 12 shown in Fi 2 and which is marked R is placed at the top of the cylinder and the cylinder is revolved clockwise as seen by an observerstanding at the left of the said cylinder in Fig. 1. Of course, the chart is laid upon the left side of the cylinder 1() as seen by an observer in the said position.

If it is desired to test the left eye of the patient, then the end of the chart which is marked L in Fig. 2 for example, is placed at the top of the cylinder 10 as represented in Fig. 1, and the chart is now laid over the right hand side of the cylinder, as seen by an observer in the said position and the cylinder 10 is now revolved counterclockwise.

The phrases H of right eye and H of left eye appearing at the sides of the chart in Fig. 2, denote the fact that the ordinates of this chart measure the degree of hypermetropia. The expressions M of right eye and M of left eye at the bottom of the chart indicate the fact that the abscissas indicate the degree of myopia.

The horizontal line shown in the center of the chart in Fig. 2 conveniently enables the operator to determine the upper and lower halves of the chart.

The equation a=p-r is simply a duplication of the well known equation of Donders Where a equals the number ofdiopters representing the accommodation, p equals the number of diopters represented by the eye when in a state of maximum refraction, that is, at the punctum proximum and r equals the'number of diopters represented by the eye in a condition of rest, that is, at the punctum remotum. Hence p equals the dynamic refraction of the eye and r the static refraction.

The vertical lines on the chart correspond to the successive positions in which the object viewed can be placed. There are sixteen positions thus indicated in the chart shown in Fig. 2b, showing that the object viewed can be placed in a greater number of successive positions than in the diagrammatic representation shown in Fig. 1. The horizontal lines of the chart shown in Fig. 2 for example, conveniently enable the operator to judge the character of the graph secured.

`trated which havebeen taken from actual practice.'

'ator ycan immediatelyfascertain the fact thatr In Fig'. 2b `a number of graphs are-illusf For example, the ygraph' B indicates ai 'myopie right eye and the graph F indicates all myopie left eye of'the'sam'e man.'` The oper-y the eyes thus tested lare l'myopie because these graphs are inclined downwardly quitesharp* 4 ly and their bottom points are consider` ablybelow the middle horizontal lin'e "of the cha-rt.4- -w 1- i- -w Itf is' veryA importanti in lorder tol correctly 'accommodate for `thei ldefectsy in 'vision, to

ascertain the? true' binocular axis. This 'is determined'bythe varying powers at varying -distances ofthetwo'eye's of the patient. 'To vdetermine the binocular axis, I take for purbetween the twoends of the graphy 'BL' These intersect in the'point 0;

A similar line H is now 'drawn between theI starting point 'ofgraph F Iand thepointof said graph immediatelypreceding lthe end point thereof. Asimilar line lis "now drawn to ac'orre'spondingI preceding point on the graph B. The lines 'G and A intersect inthe point A andthe line 0 `can now be secured by drawing' 'aI line fconnecting` the points A0 and C? and the angle between the line 0 and 0 indicates the `deviation ofthe principal binocular axis'of the patient.

Other tests made of a child elevenlyears'o age having perfect visionresulted asv follows: y V

The graph N was securedwhen the ychild viewed a black doty on a sheet of paper as 'different results are secured `when the patients vision is forced by means of a bright luminous object. The graph I was securedy when the said patient looked atia luminous object such as the screen having the luminous v slit illuminated by the electric light before mentioned These graphs "illustrate that when the eye is looking at a bright'light the pupil contracts and therefore the accommo- V dation of the eye is changed. vItsr refractive powers are changed by the` contraction of the pupil in order to prevent too much light" entering the eye and irritating or Iinjuring the nerves. I e `v The point P which is the'intersection of the line P with the axisl 0, indicates the accommodative powersvofthe eye when gazing at a relatively dull 4object and the pointK formed by the intersection vof the line K with I' the axis 0, indicates the accommodative powers of the eye when gazing at a relatively bright andy luminous lobject. SinceV both eyes of the child were perfect, these 'two @points werethe saniein' both eyes and hence the binocular" axis" would 'coincide vwith -the line The line having the two ends and Y'which isiparalle'lto the horizontal lines of the' chart is ag'raphfshowing that thev child Awas' suffering "from neither fstrabi's'mus nor astigmatism and that thelmonocular axis' 'of either Keye didnot deviate lin any direction.

It makes no difference for the`l purposes of my invention 'ifthe 'said line wouldbe in any other part ofthe 'chart andthe length thereofcoul'doorr'espond tothe distance between the two pencils or otherindicating means '46' and'4`6f which are adjacent the" member' 46 beforementioned."

Asvindicated diagrammatically` in Fig. 3,

these mernbe'rs-46l and '46 indicate the move-l ment of the prisms before mentioned in order to determine strab'ismus cr astigmatism. e

vAs'before mentioned5 theiastigmatism of the patient isfdetermined'by revolving the framey containing the lenses around a `central imaginary axis whichis perpendicular to the piane` of the paper in Fig; 9.

In lorder to determine' strabismus itl is necessary to befable'to revolve the said frame yabout the two other fundamental axes' as indicated in Fig. 3.and th'e'members 46 and 46 `are provided so asI 'to'v record the movement of the `said frame on the said twoaxes. Thus'the pencil 46 vwhich is mounted upon the crosspiece 81 is lconnected by clamping nut 88 to vertical member88, and by said member 88 to the Ufshaped frame lmember 82,

whereby when the set screw 48 loosened from member 49 andthe frame 1s revolved about the vertical axis located 1n the plane f 'of the paper'in Fig.4 9,. the said pencil. 46

describes an arc which can berecordedv on the chart on cylinder 10. When the pencil 46 is being thus actuated, the paper is around the drum as before mentioned, anda lseries of points can be'securled by upwardly moving the cylinderIO as 'before mentioned,y but the' graph describedl by .the'pencil or similar member 46 does not run parallel to the top line of the cylinder I or to the axis thereof 'but instead runs in a direction' substantially perpendicular thereto. v l

' In order to determinethe .compound strabismusand 'as indicated' in Fig. 35 it is necessary to indicateand record the revolution of the Iframe 4 containing the prisms,around a horizontal axis parallel toy theplane ofthe paper in Fig. 9. For this purpose, the frame 4f is' vmounted 'on-a: horizontal shaft 81 which 'can be revolved by means of the knurled knob 43.' This knob 43 is provided with an eccentric 7 8 which is rigid' with the said shaft '81l on which the frame 4 is m/ounted. An

angle arm 79 'is provided with a"perforation l8() with which said'A 'eccentric 78 cooperates so that saidarm 79 '11S revolved about a, vertical axis in the plane of the paper of Fig. 9, when the knob 43 is turned.

When arm 79 is thus actuated by the eccentric 78, it causes the revolution of the member 76 about a vertical axis in the plane of the paper in Fig. 9, because the member 79 is secured to member 76 by a stud or rivet 83. The penior similar member 46 is connected to the cross-piece 75 into which the frame member 76 is pressed so that the two move together.

By means ofthis mechanism, the pencils 46 and 46 move when the frame member 4 and the priins are revolved about a vertical axis in the plane of Fig. 9 and the pencil or similar member 46 alone moves when the frame 4 is revolved about a horizontal axis in Fig. 9-

A graph illustrating liypermetropia on the chart begins from the zero point as all the graphs start from this point but instead of bending down to the bottom of the chart, it would end relatively much nearer to the central horizontal line of the chart.

The operator can be provided with a chart similar to that shown in Fig. 2, but made of transparent material suoli as celluloid and haviiigvarious indicia marked thereon, so that by placing said celluloid chart on the test chart the operator can ascertain the defects in the accommodation of the eye or eyes tested.

The diagonal lines seen on the chart 12 in Fig. 2 are derived as follows:

If a White screen is placed at the position marked 0 adjacent the eye of the patient in Fig. 1 `and the lamp is held at the position marked 0 on the lamp scale, then thcliolder -caii be moved to a position in which a single luminous point will be visible upon the said screen, this point being the result of the convergence of the live pencils of light that. pass through the five openings in the screen 2.

If now the luminous object is moved to the position marked l on the lamp scale, then the holder having the prisms therein will have to be moved to the leftgof the first position in order to produce the singlel luminous point before mentioned. In this manner a series of records can be made upon a chart suitably placed upon the cylinder 10 as before mentioned, but the test is now being made with a white screen instead of the eye of the patient.

If now, the successive distances between the holder, and the said white screen be reduced to inches or diopters these diopters can be used for indicating the ordinates of the said chart. The zero axis can be the top horizontal line shown in Fig. 2. The distance in inches or diopters which the luminous ob- .ject is moved from the original zero position can beI laid as abscissas on the said chart, the

zero line being the left-hand line or the righthand line of the said chart.

Experiments have shown that the graphs illustrating the movement of the said holder 4 for a given set of prisms have a definite angle, is `indicated by the diagonal lines drawn on the chart in Fig. 2, one of these lines being drawn for purposes of comparison with the left eye of the patient, and the other line being drawn for purposes of comparison with the right eye ofthe patient and these two upper and lower pencils of light issuing from the luminous object is measured, at each interval, and the angle of the said pencils or beams of light after they have passed through the prisms is also measured, then the difference between the two angles shows the accommodation effort of the eye, whether muscular or refractive. At the region or zone of poorest vision, the patients eye will show the least i variation in accommodation, for 'a given movement of the object viewed.

For example, in an actual test made with the luminous point, and with prisms of a given angle, when the luminous object was eleven inches ,away from the prisms, the upper and lower pencils of light to the centers of the'upper and lower prisms made an angle of 10 28. After passing through the said prisms, these rays of light had an angle of 9 34. Hence the eye tested had to display an accomniodative power of 54. l/Vlieii the luminous object was twelye inches away the angle made by the said beams of light falling upon the prisms was 9 34 and the angle of the beams of light refracted by the prisms was 10 28 so that the accommodative power was now minus 54. This lastmentioned testwas made with a perfect eye, namely, the eye of the child of eleven years of age before-mentioned, and hence this point of zero accommodation of the eye would occur at different parts of the test, depending as to whether the patient. was myopie or hypermetropic.

Conventional mechanism such as a broken gear on shaft 11 and a vertical rack which engaged the said gear only when said shaft was moved by the cani could be used for automatically revolving said shaft.

Although in most cases, the position of the eye will be between'the point of convergence of the light rays and the prisms, in some tests, it may be necessary to have the said eye at a definite distance to the left of the said point of convergence 7 in order to be able to see the five images,

It yisy understood that k,altho'ughf I have shown prisms or 'refractive'bodies for creat# ing the series of images, that any other equivalent optical meansmay be- -used for creating a series of images.

Since thel glass used for the refracting" bodies is preferably chromatic, images are formed in a seriesof coloi's so that ya suitable test canA be made i-f the eye of the patient 1sv color blind to one or more colors.

The chart shown in Fig. 2b has its ordinates and abscissas in inches, although of course they could express diopters. To find the"limit of binocular accommodation, beyondwhich y the eyes squint, chords A and G are drawn to graphs 'B and F, which illustrate the abnor-V mal eyes tested. The binocular axis 0 is determined as vbefore` described. The lengthof the projection of 0 lon 0 from their point of intersection to the point of intersection of 0 With'A and G expresses said limit of binocular accommodation. If the chart were drawn in a scale of diopters, then the graphs would be substantially straight lines, coinciding with said. chords, so that it would not be necessary to draw them.

I have shown preferred embodiments of my invention, but it is clear that numerous changes andl omissions could be made without departing from its spirit.

I claim:

1. A'metliod of testing the refractive power of an eye which consists in causing an object to create a series of images by causing the light raysissuing from said object to be separated by bodies which change the directions of said rays and then moving the saidvobject and said bodies through a series of consecutive positions at each of which the eyepof the patient is kept in substantially the saine position to view the said series of images. i

2. A method of testing the refractive powers of an eye which consists in causing i the light rays from an object to pass through aseries of prisms symmetrically disposed with respect to a central point and also permitting the said light rays to pass through said central point, and then moving the said object and the said prisms through a series of consecutive positions While the eye of the patient `is held in substantially the same position, the

consecutive positions of the said prisms being vdetermined by the point at which the eye of held: substantially stationary for seeing the said images, and recording each position. of' the said refractin I bodies upona chart which is moved in a direction transverse to the move` nient of said refracting bodies, eachv said transverse movement of the said chart corresponding to the movement of the said object, whereby a graph is secured to illustrate the condition of the eye. i c i 5. In the art of testing vision by causing l the eye which is being tested to view 'a series' Y of imagesproduced by passing beams of light through a series of bodies, that step, in the artwhich consists in determining strabismus lby revolving the said refracting bodies until the eye being tested sees a maximum number of images.

6. In the art of testing vision by causing the eye which is being tested to view a series of images produced by causing the light issuing froin an object to pass through a series of refracting bodies, that step in the art which consists in recording the condition of strabismus by revolving'the said refracting bodies until the eye which is being tested sees a maximum number of images, and recording the movement 'of the said refracting bodies.

7. In the art of detecting vision, that step in the art which consists in determining the axis of astigmatism of the patient by causing the eye of the patient to View a series of images produced by causing the light issuing from the object viewed, to pass through a series. of refracting bodies and separately destroying pairs of such images by suitably shutting of the light rays transmitted to said refracting bodies to the eyes of the patient.

8. In the art of testing vision, that step in the ait which consists in recording a series of points according to the method of claim 4 upon a chart whose ordinates and Whose abscissas are expressed in diopters.

9. In the art of testing vision,"that step in the art which consists in recording a series of points according to the method of claim 4 upon a chart, the diagonal lines of which chart are graphs expressing the relationship between the position of the luminous object and the point of convergence of the light rays which have passed through the said refracting bodies.

1 0. A method of testingl the refractive power of an eye according to claim l, which\ consists in causing the said light rays to pass through a series of refracting bodies made of chromatic glass.

l1. A method of determining the true binocular axis of a patients eyes, which consists in producing graphs illustrating the condition of the said eyes according to the method of claim 4 so that the said graphs intersect eachother, and then connecting the ends of the said graphs With a series of like points on each of said graphs, whereby the true binocular axis can be found by connecting'the points of intersection of the said connecting lines.

12. A method of determining the limit of binocular accommodation of a person which consists in causing an object to produce a series of images by means of refracting bodies, moving the said object to a series of consecutive positions, moving the said refracting bodies to Va series of consecutive positions While the eye of the patient is held substantially stationary for seeing the said images, recording each position of the said refracting bodies by means of points upon a chart Which is moved in a direction transverse to the movement of the said refracting bodies, connecting the corresponding points by means of lines to produce on said chart diagonal intersecting and symmetrically located graphs expressing the relationship between the position of the luminous object and thepoint of convergence of the light rays which have passed through the said refracting bodies, determining the true binocular axis, and projecting on the normal binocular axis that length of said true binocular axis which is between the intersection of said `axes and the intersection of said true binocular axis With the chords of said graphs.

In testimony whereof I hereunto alix my signature.

JACOB Z. A. DENINSGN. 

